<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .wrap{

            margin: 0 auto;

            width: 80%;

        }

        #left{

            width: 200px;
            height: 500px;
            background-color: #ff4b59;

            float: left;

           margin-left: -100%;

        }

        #right{

            width: 200px;
            height: 500px;
            background-color: olivedrab;

            float: left;

           margin-left: -200px;


        }

        #main{


            width: 100%;
            background-color: #B0B0B0;

            float: left;


        }

        .content{

            height: 500px;


        }


    </style>
</head>
<body>

<div class="wrap">
    <section id="main">

        <div class="content">content</div>

    </section>
    <aside id="left">left</aside>
    <aside id="right">right</aside>

</div>

</body>
</html>